In the UK we have to put milk in our "bitter tasting" mass produced factory tea, to make it less bitter, the alkaline in the milk counteracts the bitter taste of the tea. This problem does not apply so much in other tea producing countries where tea can be drunk and remain refreshing without the need to add milk. It is possible to buy less bitter tasting tea but in general all the shops and supermarkets sell the global mass produced brands. Also English tea tends to be stronger than some other lighter more exotic foreign blends. 

You can easily tell if it is an inferior bitter blend if you see a scum on the top of the tea, or a layer floating on the top of what looks like "tea dust' produced by factory production.

In the United States, tea is often drunk without milk. I was surprised when we visited England decades ago and learned that everyone puts milk and sugar in their tea.

In the summer, we often drink iced tea which is cold--with ice cubes floating in it--and often heavily sweetened. We usually drink it without milk in it.

I don't know exactly what "milk tea" is like.

Recently, some of the coffee chains have begun offering tea, and Starbucks, for example, offers a "chai tea latte" which is sweet and milky, and has the peppery "chai tea" taste.

Very recently, some places have started to offer "bubble tea" or "boba tea" which is a cold, sweet drink that has tapioca "pearls" in it. I don't know much about it. I've only had it twice. It is growing in popularity. On a local Facebook page somebody complained that there wasn't any place to get it in our town, and that they had to drive 10 km. to get it.